Differential silicon oxide etch

ABSTRACT

A method of etching exposed silicon oxide on patterned heterogeneous structures is described and includes a gas phase etch created from a remote plasma etch. The remote plasma excites a fluorine-containing precursor. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents combine with water vapor. Reactants thereby produced etch the patterned heterogeneous structures to remove two separate regions of differing silicon oxide at different etch rates. The methods may be used to remove low density silicon oxide while removing less high density silicon oxide.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Prov. Pat. App. No.61/701,964 filed Sep. 17, 2012, and titled “DIFFERENTIAL SILICON OXIDEETCH,” which is hereby incorporated herein in its entirety by referencefor all purposes.

BACKGROUND OF THE INVENTION

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess which etches one material faster than another helping e.g. apattern transfer process proceed. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits and processes, etch processes have been developedwith a selectivity towards a variety of materials.

A wet HF etch preferentially removes silicon oxide over otherdielectrics and semiconductors. However, wet processes are unable topenetrate some constrained trenches and sometimes deform the remainingmaterial. Dry etches produced in local plasmas (plasmas within thesubstrate processing region) can penetrate more constrained trenches andexhibit less deformation of delicate remaining structures. However,local plasmas can damage the substrate through the production ofelectric arcs as they discharge.

A Siconi™ etch is a remote plasma assisted dry etch process whichinvolves the simultaneous exposure of a substrate to H₂, NF₃ and NH₃plasma by-products. Remote plasma excitation of the hydrogen andfluorine species allows plasma-damage-free substrate processing. TheSiconi™ etch is largely conformal and selective towards silicon oxidelayers but does not readily etch silicon regardless of whether thesilicon is amorphous, crystalline or polycrystalline. Silicon nitride istypically etched at a rate between silicon and silicon oxide.

Methods are needed to progressively expand this suite of selectivitiesin order to enable novel process flows.

BRIEF SUMMARY OF THE INVENTION

A method of etching exposed silicon oxide on patterned heterogeneousstructures is described and includes a gas phase etch created from aremote plasma etch. The remote plasma excites a fluorine-containingprecursor. Plasma effluents from the remote plasma are flowed into asubstrate processing region where the plasma effluents combine withwater vapor. Reactants thereby produced etch the patterned heterogeneousstructures to remove two separate regions of differing silicon oxide atdifferent etch rates. The methods may be used to remove low densitysilicon oxide while removing less high density silicon oxide.

Embodiments of the invention include methods of etching patternedsubstrates in a substrate processing region of a substrate processingchamber. The patterned substrates have exposed silicon oxide regions.The methods include flowing a fluorine-containing precursor into aremote plasma region fluidly coupled to the substrate processing regionwhile forming a remote plasma in the remote plasma region to produceplasma effluents. The methods further include flowing water vapor intothe substrate processing region without first passing the water vaporthrough the remote plasma region. The methods further include etchingthe exposed silicon oxide regions by flowing the plasma effluents intothe substrate processing region. The exposed silicon oxide regionscomprise a first silicon oxide region having a first density and asecond silicon oxide region having a second density. The first densityis less than the second density. The first silicon oxide region etchesat a first etch rate and the second silicon oxide region etches at asecond etch rate which is lower than the first etch rate.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the disclosed embodiments. The features andadvantages of the disclosed embodiments may be realized and attained bymeans of the instrumentalities, combinations, and methods described inthe specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedembodiments may be realized by reference to the remaining portions ofthe specification and the drawings.

FIG. 1 is a flow chart of a silicon oxide selective etch processaccording to disclosed embodiments.

FIG. 2A shows a substrate processing chamber according to embodiments ofthe invention.

FIG. 2B shows a showerhead of a substrate processing chamber accordingto embodiments of the invention.

FIG. 3 shows a substrate processing system according to embodiments ofthe invention.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION OF THE INVENTION

A method of etching exposed silicon oxide on patterned heterogeneousstructures is described and includes a gas phase etch created from aremote plasma etch. The remote plasma excites a fluorine-containingprecursor. Plasma effluents from the remote plasma are flowed into asubstrate processing region where the plasma effluents combine withwater vapor. Reactants thereby produced etch the patterned heterogeneousstructures to remove two separate regions of differing silicon oxide atdifferent etch rates. The methods may be used to remove low densitysilicon oxide while removing less high density silicon oxide.

Selective remote gas phase etch processes have used a hydrogen source ofammonia (NH₃) and a fluorine source of nitrogen trifluoride (NF₃) whichtogether flow through a remote plasma system (RPS) and into a reactionregion. The flow rates of ammonia and nitrogen trifluoride are typicallychosen such that the atomic flow rate of hydrogen is roughly twice thatof fluorine in order to efficiently utilize the constituents of the twoprocess gases. The presence of hydrogen and fluorine allows theformation of solid byproducts of (NH₄)₂SiF₆ at relatively low substratetemperatures. The solid byproducts are removed by raising thetemperature of the substrate above the sublimation temperature. Remotegas phase etch processes remove oxide films much more rapidly than, e.g.silicon. However, there is very little difference among etch ratesbetween different preparations of silicon oxide. The inventors havediscovered that the selectivity of low density silicon oxide over highdensity silicon nitride can be enhanced by exciting afluorine-containing precursor in a remote plasma and combining theplasma effluents with water vapor which has not passed through a remoteplasma system.

In order to better understand and appreciate the invention, reference isnow made to FIG. 1 which is a flow chart of a silicon oxide selectiveetch process according to disclosed embodiments. Prior to the firstoperation, the substrate is patterned and a high density silicon oxideis deposited onto the patterned substrate. A low density silicon oxideis then deposited over the high density silicon oxide and acts as atemporary sacrificial support structure, e.g., for a delicate verticalfeature. Once the structural aspects of the low density silicon oxideare no longer needed, it can be removed with the etch process describedherein, while retaining the high density silicon oxide.

The patterned substrate is then delivered into a processing region(operation 110). A flow of nitrogen trifluoride is initiated into aplasma region separate from the processing region (operation 120). Othersources of fluorine may be used to augment or replace the nitrogentrifluoride. In general, a fluorine-containing precursor is flowed intothe plasma region and the fluorine-containing precursor comprises atleast one precursor selected from the group consisting of atomicfluorine, diatomic fluorine, nitrogen trifluoride, carbon tetrafluoride,hydrogen fluoride and xenon difluoride. The separate plasma region maybe referred to as a remote plasma region herein and may be within adistinct module from the processing chamber or a compartment within theprocessing chamber. The plasma effluents formed in the remote plasmaregion are then flowed into the substrate processing region (operation125). Water vapor is simultaneously flowed into the substrate processingregion (operation 130) to react with the plasma effluents. The watervapor is not passed through the remote plasma region and therefore isonly excited by interaction with the plasma effluents. The water vaporis not passed through any remote plasma region before entering thesubstrate processing region in embodiments of the invention.

The patterned substrate is selectively etched (operation 135) such thatthe low density silicon oxide is removed at a significantly higher ratethan the high density silicon oxide. This capability enables the use ofone silicon oxide region as a sacrificial component (the low densitysilicon oxide) at the same time another silicon oxide region is exposed(the high density silicon oxide). The reactive chemical species areremoved from the substrate processing region and then the substrate isremoved from the processing region (operation 145).

Wet etches, such as buffered oxide etches, were also used to selectivelyremove low density silicon oxide relative to high density silicon oxide.The inventors have found that the selectivity was limited to about 6:1or 7:1 (low density SiO etch rate:high density SiO etch rate). Using thegas phase dry etch processes described herein, the inventors haveestablished that selectivities of 40:1 and even 50:1 (low density SiOetch rate:high density SiO etch rate) are possible. The low-densitysilicon oxide etch rate exceeds the high-density silicon oxide etch rateby a multiplicative factor of about 8 or more, about 10 or more, about15 or more, or about 25 or more, in embodiments of the invention.

Examplary deposition techniques which result in low density siliconoxide include chemical vapor deposition using dichlorosilane as adeposition precursor, spin-on glass (SOG) or plasma-enhanced chemicalvapor deposition. High density silicon oxide may be deposited as thermaloxide (exposing silicon to, e.g., O₂ at high temperature), disilaneprecursor furnace oxidation or high-density plasma chemical vapordeposition in embodiments of the invention.

Gas phase etches involving only fluorine (either remote or local) do notpossess the selectivity needed to remove the low-density silicon oxidewhile leaving other portions of the patterned substrate (made ofhigh-density silicon oxide) nearly undisturbed. The gas phase etchesdescribed herein have an added benefit, in that they do not producesolid residue. Elimination of solid residue avoids disturbing delicatefeatures which may be supported by the sacrificial low-density siliconoxide. Elimination of solid residue also simplifies the process flowsand decreases processing costs by removing the sublimation step. Thefluorine-containing precursor is devoid of hydrogen in embodiments ofthe invention. The plasma effluents may also be devoid of hydrogen whenno hydrogen precursors are included in the remote plasma region. Thisensures no possible production of solid by-products on the patternedsubstrate.

Without wishing to bind the coverage of the claims to theoreticalmechanisms which may or may not be entirely correct, some discussion ofpossible mechanisms may prove beneficial. Radical-fluorine precursorsare produced by delivering a fluorine-containing precursor into theremote plasma region. Applicants suppose that a concentration offluorine ions and atoms is produced and delivered into the substrateprocessing region. Water vapor (H₂O) may react with the fluorine toproduce less reactive species such as HF₂ ⁻ which still readily removelow-density silicon oxide but do not readily remove high-density siliconoxide from the patterned substrate surface. The selectivity combinedwith the lack of solid residue byproducts, make these etch processeswell suited for removing molds and other silicon oxide supportstructures from delicate non-silicon oxide materials while inducinglittle deformation in the remaining delicate structures.

The pressure in the substrate processing region may be above or about0.1 Torr and less than or about 50 Torr, in disclosed embodiments,during the etching operation. The pressure within the substrateprocessing region may also be below or about 40 Torr and above or about5 Torr or 10 Torr in disclosed embodiments. Any of the upper limits canbe combined with any of these lower limits to form additionalembodiments of the invention. The temperature of the patterned substratemay be about 0° C. or more and about 100° C. or less, in disclosedembodiments, during the etching operation. The temperature of thepatterned substrate may be about 5° C. or more and about 40° C. or lessduring the etching operation in embodiments of the invention.

Additional water vapor and remotely-excited-fluorine etch processparameters are disclosed in the course of describing an exemplaryprocessing chamber and system.

Exemplary Processing System

Processing chambers that may implement embodiments of the presentinvention may be included within processing platforms such as theCENTURA® and PRODUCER® systems, available from Applied Materials, Inc.of Santa Clara, Calif. Examples of substrate processing chambers thatcan be used with exemplary methods of the invention may include thoseshown and described in co-assigned U.S. Provisional Patent App. No.60/803,499 to Lubomirsky et al, filed May 30, 2006, and titled “PROCESSCHAMBER FOR DIELECTRIC GAPFILL,” the entire contents of which is hereinincorporated by reference for all purposes. Additional exemplary systemsmay include those shown and described in U.S. Pat. Nos. 6,387,207 and6,830,624, which are also incorporated herein by reference for allpurposes.

FIG. 2A is a substrate processing chamber 1001 according to disclosedembodiments. A remote plasma system (RPS 1010) may process thefluorine-containing precursor which then travels through a gas inletassembly 1011. Two distinct gas supply channels are visible within thegas inlet assembly 1011. A first channel 1012 carries a gas that passesthrough the remote plasma system RPS 1010, while a second channel 1013bypasses the RPS 1010. Either channel may be used for thefluorine-containing precursor, in embodiments. On the other hand, thefirst channel 202 may be used for the process gas and the second channel1013 may be used for a treatment gas. The lid 1021 (e.g. a conductingtop portion) and a perforated partition (showerhead 1053) are shown withan insulating ring 1024 in between, which allows an AC potential to beapplied to the lid 1021 relative to showerhead 1053. The AC potentialstrikes a plasma in chamber plasma region 1020. The process gas maytravel through first channel 1012 into chamber plasma region 1020 andmay be excited by a plasma in chamber plasma region 1020 alone or incombination with RPS 1010. If the process gas (the fluorine-containingprecursor) flows through second channel 1013, then only the chamberplasma region 1020 is used for excitation. The combination of chamberplasma region 1020 and/or RPS 1010 may be referred to as a remote plasmasystem herein. The perforated partition (also referred to as ashowerhead) 1053 separates chamber plasma region 1020 from a substrateprocessing region 1070 beneath showerhead 1053. Showerhead 1053 allows aplasma present in chamber plasma region 1020 to avoid directly excitinggases in substrate processing region 1070, while still allowing excitedspecies to travel from chamber plasma region 1020 into substrateprocessing region 1070.

Showerhead 1053 is positioned between chamber plasma region 1020 andsubstrate processing region 1070 and allows plasma effluents (excitedderivatives of precursors or other gases) created within RPS 1010 and/orchamber plasma region 1020 to pass through a plurality of through-holes1056 that traverse the thickness of the plate. The showerhead 1053 alsohas one or more hollow volumes 1051 which can be filled with a precursorin the form of a vapor or gas (such as a silicon-containing precursor)and pass through small holes 1055 into substrate processing region 1070but not directly into chamber plasma region 1020. Showerhead 1053 isthicker than the length of the smallest diameter 1050 of thethrough-holes 1056 in this disclosed embodiment. In order to maintain asignificant concentration of excited species penetrating from chamberplasma region 1020 to substrate processing region 1070, the length 1026of the smallest diameter 1050 of the through-holes may be restricted byforming larger diameter portions of through-holes 1056 part way throughthe showerhead 1053. The length of the smallest diameter 1050 of thethrough-holes 1056 may be the same order of magnitude as the smallestdiameter of the through-holes 1056 or less in disclosed embodiments.

In the embodiment shown, showerhead 1053 may distribute (viathrough-holes 1056) process gases which contain oxygen, hydrogen and/ornitrogen and/or plasma effluents of such process gases upon excitationby a plasma in chamber plasma region 1020. In embodiments, the processgas introduced into the RPS 1010 and/or chamber plasma region 1020through first channel 1012 may contain fluorine (e.g. CF₄, NF₃ or XeF₂).The process gas may also include a carrier gas such as helium, argon,nitrogen (N₂), etc. Plasma effluents may include ionized or neutralderivatives of the process gas and may also be referred to herein as aradical-fluorine precursor referring to the atomic constituent of theprocess gas introduced.

In embodiments, the number of through-holes 1056 may be between about 60and about 2000. Through-holes 1056 may have a variety of shapes but aremost easily made round. The smallest diameter 1050 of through-holes 1056may be between about 0.5 mm and about 20 mm or between about 1 mm andabout 6 mm in disclosed embodiments. There is also latitude in choosingthe cross-sectional shape of through-holes, which may be made conical,cylindrical or a combination of the two shapes. The number of smallholes 1055 used to introduce a gas into substrate processing region 1070may be between about 100 and about 5000 or between about 500 and about2000 in different embodiments. The diameter of the small holes 1055 maybe between about 0.1 mm and about 2 mm.

FIG. 2B is a bottom view of a showerhead 1053 for use with a processingchamber according to disclosed embodiments. Showerhead 1053 correspondswith the showerhead shown in FIG. 2A. Through-holes 1056 are depictedwith a larger inner-diameter (ID) on the bottom of showerhead 1053 and asmaller ID at the top. Small holes 1055 are distributed substantiallyevenly over the surface of the showerhead, even amongst thethrough-holes 1056 which helps to provide more even mixing than otherembodiments described herein. A fluorine-containing precursor may beflowed through through-holes 1056 in dual-zone showerhead 1053 whilewater vapor passes through separate zones in the dual-zone showerheadentering the substrate processing region through small holes 1055. Theseparate zones open into the substrate processing region but not intothe remote plasma region.

An exemplary patterned substrate may be supported by a pedestal (notshown) within substrate processing region 1070 when fluorine-containingplasma effluents arriving through through-holes 1056 in showerhead 1053combine with moisture arriving through the small holes 1055 originatingfrom hollow volumes 1051. Though substrate processing region 1070 may beequipped to support a plasma for other processes such as curing, noplasma is present during the etching of patterned substrate, inembodiments of the invention.

A plasma may be ignited either in chamber plasma region 1020 aboveshowerhead 1053 or substrate processing region 1070 below showerhead1053. A plasma is present in chamber plasma region 1020 to produce theradical-fluorine precursors from an inflow of the fluorine-containingprecursor. An AC voltage typically in the radio frequency (RF) range isapplied between the conductive top portion 1021 of the processingchamber and showerhead 1053 to ignite a plasma in chamber plasma region1020 during deposition. An RF power supply generates a high RF frequencyof 13.56 MHz but may also generate other frequencies alone or incombination with the 13.56 MHz frequency.

The top plasma may be left at low or no power when the bottom plasma inthe substrate processing region 1070 is turned on to clean the interiorsurfaces bordering substrate processing region 1070. A plasma insubstrate processing region 1070 is ignited by applying an AC voltagebetween showerhead 1053 and the pedestal or bottom of the chamber. Acleaning gas may be introduced into substrate processing region 1070while the plasma is present.

The pedestal may have a heat exchange channel through which a heatexchange fluid flows to control the temperature of the substrate. Thisconfiguration allows the substrate temperature to be cooled or heated tomaintain relatively low temperatures (from room temperature throughabout 120° C.). The heat exchange fluid may comprise ethylene glycol andwater. The wafer support platter of the pedestal (preferably aluminum,ceramic, or a combination thereof) may also be resistively heated inorder to achieve relatively high temperatures (from about 120° C.through about 1100° C.) using an embedded single-loop embedded heaterelement configured to make two full turns in the form of parallelconcentric circles. An outer portion of the heater element may runadjacent to a perimeter of the support platter, while an inner portionruns on the path of a concentric circle having a smaller radius. Thewiring to the heater element passes through the stem of the pedestal.

The substrate processing system is controlled by a system controller. Inan exemplary embodiment, the system controller includes a hard diskdrive, a floppy disk drive and a processor. The processor contains asingle-board computer (SBC), analog and digital input/output boards,interface boards and stepper motor controller boards. Various parts ofCVD system conform to the Versa Modular European (VME) standard whichdefines board, card cage, and connector dimensions and types. The VMEstandard also defines the bus structure as having a 16-bit data bus anda 24-bit address bus.

The system controller controls all of the activities of the etchingchamber. The system controller executes system control software, whichis a computer program stored in a computer-readable medium. Preferably,the medium is a hard disk drive, but the medium may also be other kindsof memory. The computer program includes sets of instructions thatdictate the timing, mixture of gases, chamber pressure, chambertemperature, RF power levels, susceptor position, and other parametersof a particular process. Other computer programs stored on other memorydevices including, for example, a floppy disk or other anotherappropriate drive, may also be used to instruct the system controller.

A process for differentially etching low-density silicon oxide andhigh-density silicon oxide on a substrate or a process for cleaning achamber can be implemented using a computer program product that isexecuted by the system controller. The computer program code can bewritten in any conventional computer readable programming language: forexample, assembly language, C, C++, Pascal, Fortran or others. Suitableprogram code is entered into a single file, or multiple files, using aconventional text editor, and stored or embodied in a computer usablemedium, such as a memory system of the computer. If the entered codetext is in a high level language, the code is compiled, and theresultant compiler code is then linked with an object code ofprecompiled Microsoft Windows® library routines. To execute the linked,compiled object code the system user invokes the object code, causingthe computer system to load the code in memory. The CPU then reads andexecutes the code to perform the tasks identified in the program.

The interface between a user and the controller is via a flat-paneltouch-sensitive monitor. In the preferred embodiment two monitors areused, one mounted in the clean room wall for the operators and the otherbehind the wall for the service technicians. The two monitors maysimultaneously display the same information, in which case only oneaccepts input at a time. To select a particular screen or function, theoperator touches a designated area of the touch-sensitive monitor. Thetouched area changes its highlighted color, or a new menu or screen isdisplayed, confirming communication between the operator and thetouch-sensitive monitor. Other devices, such as a keyboard, mouse, orother pointing or communication device, may be used instead of or inaddition to the touch-sensitive monitor to allow the user to communicatewith the system controller.

The chamber plasma region or a region in an RPS may be referred to as aremote plasma region. In embodiments, the radical precursor (e.g. aradical-fluorine precursor) is created in the remote plasma region andtravels into the substrate processing region to combine with the watervapor. In embodiments, the water vapor is excited only by theradical-fluorine precursor (aka the plasma effluents). Plasma power mayessentially be applied only to the chamber plasma region, inembodiments, to ensure that the radical-fluorine precursor provides thedominant excitation to the water vapor.

In embodiments employing a chamber plasma region, the excited plasmaeffluents are generated in a section of the substrate processing regionpartitioned from a deposition region. The deposition region, also knownherein as the substrate processing region, is where the plasma effluentsmix and react with the water vapor to etch the patterned substrate(e.g., a semiconductor wafer). The excited plasma effluents may also beaccompanied by inert gases (in the exemplary case, argon). The watervapor does not pass through a plasma before entering the substrateplasma region, in embodiments. The substrate processing region may bedescribed herein as “plasma-free” during the etching operation of thepatterned substrate. “Plasma-free” does not necessarily mean the regionis devoid of plasma. Ionized species and free electrons created withinthe plasma region do travel through pores (apertures) in the partition(showerhead) but the water vapor is not substantially excited by theplasma power applied to the plasma region. The borders of the plasma inthe chamber plasma region are hard to define and may encroach upon thesubstrate processing region through the apertures in the showerhead. Inthe case of an inductively-coupled plasma, a small amount of ionizationmay be effected within the substrate processing region directly.Furthermore, a low intensity plasma may be created in the substrateprocessing region without eliminating desirable features of the formingfilm. All causes for a plasma having much lower intensity ion densitythan the chamber plasma region (or a remote plasma region, for thatmatter) during the creation of the excited plasma effluents do notdeviate from the scope of “plasma-free” as used herein.

Nitrogen trifluoride (or another fluorine-containing precursor) may beflowed into chamber plasma region 1020 at rates between about 25 sccmand about 200 sccm, between about 50 sccm and about 150 sccm or betweenabout 75 sccm and about 125 sccm in different embodiments. Water vapormay be flowed into substrate processing region 1070 at rates betweenabout 25 sccm and about 200 sccm, between about 50 sccm and about 150sccm or between about 75 sccm and about 125 sccm in differentembodiments.

Combined flow rates of water vapor and fluorine-containing precursorinto the chamber may account for 0.05% to about 20% by volume of theoverall gas mixture; the remainder being carrier gases. Thefluorine-containing precursor is flowed into the remote plasma regionbut the plasma effluents has the same volumetric flow ratio, inembodiments. In the case of the fluorine-containing precursor, a purgeor carrier gas may be first initiated into the remote plasma regionbefore those of the fluorine-containing gas to stabilize the pressurewithin the remote plasma region.

Plasma power can be a variety of frequencies or a combination ofmultiple frequencies. In the exemplary processing system the plasma isprovided by RF power delivered to lid 1021 relative to showerhead 1053.The RF power may be between about 10 watts and about 2000 watts, betweenabout 100 watts and about 2000 watts, between about 200 watts and about1500 watts or between about 500 watts and about 1000 watts in differentembodiments. The RF frequency applied in the exemplary processing systemmay be low RF frequencies less than about 200 kHz, high RF frequenciesbetween about 10 MHz and about 15 MHz or microwave frequencies greaterthan or about 1 GHz in different embodiments. The plasma power may becapacitively-coupled (CCP) or inductively-coupled (ICP) into the remoteplasma region.

Substrate processing region 1070 can be maintained at a variety ofpressures during the flow of water vapor, any carrier gases and plasmaeffluents into substrate processing region 1070. The pressure may bemaintained between about 500 mTorr and about 30 Torr, between about 1Torr and about 20 Torr or between about 5 Torr and about 15 Torr indifferent embodiments.

In one or more embodiments, the substrate processing chamber 1001 can beintegrated into a variety of multi-processing platforms, including theProducer™ GT, Centura™ AP and Endura™ platforms available from AppliedMaterials, Inc. located in Santa Clara, Calif. Such a processingplatform is capable of performing several processing operations withoutbreaking vacuum. Processing chambers that may implement embodiments ofthe present invention may include dielectric etch chambers or a varietyof chemical vapor deposition chambers, among other types of chambers.

Embodiments of the deposition systems may be incorporated into largerfabrication systems for producing integrated circuit chips. FIG. 3 showsone such system 1101 of deposition, baking and curing chambers accordingto disclosed embodiments. In the figure, a pair of FOUPs (front openingunified pods) 1102 supply substrate substrates (e.g., 300 mm diameterwafers) that are received by robotic arms 1104 and placed into a lowpressure holding area 1106 before being placed into one of the substrateprocessing chambers 1108 a-f A second robotic arm 1110 may be used totransport the substrate wafers from the holding area 1106 to thesubstrate processing chambers 1108 a-f and back. Each substrateprocessing chamber 1108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation and othersubstrate processes.

The substrate processing chambers 1108 a-f may include one or moresystem components for depositing, annealing, curing and/or etching aflowable dielectric film on the substrate wafer. In one configuration,two pairs of the processing chamber (e.g., 1108 c-d and 1108 e-f) may beused to deposit dielectric material on the substrate, and the third pairof processing chambers (e.g., 1108 a-b) may be used to etch thedeposited dielectric. In another configuration, all three pairs ofchambers (e.g., 1108 a-f) may be configured to etch a dielectric film onthe substrate. Any one or more of the processes described may be carriedout on chamber(s) separated from the fabrication system shown indifferent embodiments.

System controller 1157 is used to control motors, valves, flowcontrollers, power supplies and other functions required to carry outprocess recipes described herein. A gas handling system 1155 may also becontrolled by system controller 1157 to introduce gases to one or all ofthe substrate processing chambers 1108 a-f. System controller 1157 mayrely on feedback from optical sensors to determine and adjust theposition of movable mechanical assemblies in gas handling system 1155and/or in substrate processing chambers 1108 a-f. Mechanical assembliesmay include the robot, throttle valves and susceptors which are moved bymotors under the control of system controller 1157.

In an exemplary embodiment, system controller 1157 includes a hard diskdrive (memory), USB ports, a floppy disk drive and a processor. Systemcontroller 1157 includes analog and digital input/output boards,interface boards and stepper motor controller boards. Various parts ofmulti-chamber processing system 1101 which contains processing chamber400 are controlled by system controller 1157. The system controllerexecutes system control software in the form of a computer programstored on computer-readable medium such as a hard disk, a floppy disk ora flash memory thumb drive. Other types of memory can also be used. Thecomputer program includes sets of instructions that dictate the timing,mixture of gases, chamber pressure, chamber temperature, RF powerlevels, susceptor position, and other parameters of a particularprocess.

A process for etching, depositing or otherwise processing a film on asubstrate or a process for cleaning chamber can be implemented using acomputer program product that is executed by the controller. Thecomputer program code can be written in any conventional computerreadable programming language: for example, 68000 assembly language, C,C++, Pascal, Fortran or others. Suitable program code is entered into asingle file, or multiple files, using a conventional text editor, andstored or embodied in a computer usable medium, such as a memory systemof the computer. If the entered code text is in a high level language,the code is compiled, and the resultant compiler code is then linkedwith an object code of precompiled Microsoft Windows® library routines.To execute the linked, compiled object code the system user invokes theobject code, causing the computer system to load the code in memory. TheCPU then reads and executes the code to perform the tasks identified inthe program.

The interface between a user and the controller may be via atouch-sensitive monitor and may also include a mouse and keyboard. Inone embodiment two monitors are used, one mounted in the clean room wallfor the operators and the other behind the wall for the servicetechnicians. The two monitors may simultaneously display the sameinformation, in which case only one is configured to accept input at atime. To select a particular screen or function, the operator touches adesignated area on the display screen with a finger or the mouse. Thetouched area changes its highlighted color, or a new menu or screen isdisplayed, confirming the operator's selection.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The patterned substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. Exposed “silicon oxide” of thepatterned substrate is predominantly SiO₂ but may include concentrationsof other elemental constituents such as nitrogen, hydrogen, carbon andthe like. In some embodiments, silicon oxide films etched using themethods disclosed herein consist essentially of silicon and oxygen. Theterm “precursor” is used to refer to any process gas which takes part ina reaction to either remove material from or deposit material onto asurface. “Plasma effluents” describe gas exiting from the chamber plasmaregion and entering the substrate processing region. Plasma effluentsare in an “excited state” wherein at least some of the gas molecules arein vibrationally-excited, dissociated and/or ionized states. A “radicalprecursor” is used to describe plasma effluents (a gas in an excitedstate which is exiting a plasma) which participate in a reaction toeither remove material from or deposit material on a surface. A“radical-fluorine precursor” is a radical precursor which containsfluorine but may contain other elemental constituents. The phrase “inertgas” refers to any gas which does not form chemical bonds when etchingor being incorporated into a film. Exemplary inert gases include noblegases but may include other gases so long as no chemical bonds areformed when (typically) trace amounts are trapped in a film.

The terms “gap” and “trench” are used throughout with no implicationthat the etched geometry has a large horizontal aspect ratio. Viewedfrom above the surface, trenches may appear circular, oval, polygonal,rectangular, or a variety of other shapes. A trench may be in the shapeof a moat around an island of material (e.g. a substantially cylindricalTiN pillar). The term “via” is used to refer to a low aspect ratiotrench (as viewed from above) which may or may not be filled with metalto form a vertical electrical connection. As used herein, a conformaletch process refers to a generally uniform removal of material on asurface in the same shape as the surface, i.e., the surface of theetched layer and the pre-etch surface are generally parallel. A personhaving ordinary skill in the art will recognize that the etchedinterface likely cannot be 100% conformal and thus the term “generally”allows for acceptable tolerances.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of thedisclosed embodiments. Additionally, a number of well known processesand elements have not been described in order to avoid unnecessarilyobscuring the present invention. Accordingly, the above descriptionshould not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the dielectric material”includes reference to one or more dielectric materials and equivalentsthereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

What is claimed is:
 1. A method of etching a patterned substrate in asubstrate processing region of a substrate processing chamber, whereinthe patterned substrate has exposed silicon oxide regions, the methodcomprising: flowing a fluorine-containing precursor into a remote plasmaregion fluidly coupled to the substrate processing region while forminga remote plasma in the remote plasma region to produce plasma effluents;flowing water vapor into the substrate processing region without firstpassing the water vapor through the remote plasma region; and etchingthe exposed silicon oxide regions by flowing the plasma effluents intothe substrate processing region, wherein the exposed silicon oxideregions comprise a first silicon oxide region having a first density anda second silicon oxide region having a second density, and wherein thefirst density is less than the second density and the first siliconoxide region etches at a first etch rate and the second silicon oxideregion etches at a second etch rate which is lower than the first etchrate.
 2. The method of claim 1 wherein the first silicon oxide regionwas deposited using dichlorosilane as a precursor.
 3. The method ofclaim 1 wherein the first silicon oxide region was deposited usingplasma-enhanced chemical vapor deposition.
 4. The method of claim 1wherein the second silicon oxide region was deposited using high-densityplasma chemical vapor deposition.
 5. The method of claim 1 wherein thefirst etch rate exceeds the second etch rate by a factor of about 8 ormore.
 6. The method of claim 1 wherein the first etch rate exceeds thesecond etch rate by a factor of about 15 or more.
 7. The method of claim1 wherein the first etch rate exceeds the second etch rate by a factorof about 25 or more.
 8. The method of claim 1 wherein the substrateprocessing region is plasma-free.
 9. The method of claim 1 wherein thewater vapor is not excited by any remote plasma formed outside thesubstrate processing region.
 10. The method of claim 1 wherein thefluorine-containing precursor comprises a precursor selected from thegroup consisting of atomic fluorine, diatomic fluorine, nitrogentrifluoride, carbon tetrafluoride, hydrogen fluoride and xenondifluoride.
 11. The method of claim 1 wherein the fluorine-containingprecursor and the plasma effluents are essentially devoid of hydrogen.12. The method of claim 1 wherein the fluorine-containing precursorflowed through through-holes in a dual-zone showerhead and the watervapor passes through separate zones in the dual-zone showerhead, whereinthe separate zones open into the substrate processing region but notinto the remote plasma region.
 13. The method of claim 1 wherein atemperature of the patterned substrate is greater than or about 0° C.and less than or about 100° C. during the etching operation.
 14. Themethod of claim 1 wherein a temperature of the patterned substrate isgreater than or about 5° C. and less than or about 40° C. during theetching operation.
 15. The method of claim 1 wherein a pressure withinthe substrate processing region is below or about 50 Torr and above orabout 0.1 Torr during the etching operation.
 16. The method of claim 1wherein forming a plasma in the remote plasma region to produce plasmaeffluents comprises applying RF power between about 10 watts and about2000 watts to the remote plasma region.
 17. The method of claim 1wherein a plasma in the remote plasma region is a capacitively-coupledplasma.